Manufacture of copper oxide rectifiers



Patented Dec. 1, 1931 UNITED STATES PATENT OFFICE PAUL H. GEIGER, OF ANNARBOR, MICHIGAN, ASSIGNOR '10 THE UNION SWITCH & SIGNAL COMPANY, OFSWISSVALE, PENNSYLVANIA, A. CORPORATION OF PENNSYL VANIA MANUFACTURE OFCOPPER OXIDE RECTIFIEBS No Drawing.

invention relates to the manufacture of copper oxide rectifiers of thekind disclosed and claimed in Letters Patent of the United States No.1,640,335, granted to L. O. Grondahl on August 23, 1927. One feature ofmy invention is the provision of a step 1n the manufacture of suchrectifiers whereby an electrical characteristic of the finishedrectifier may be changed.

I will describe certainprocesses embodying my invention, and will thenpoint out the novel features thereof in claims.

In the practice of my invention, the copper blanks are first cleaned inthe usual manner, preferably by diping in an acid solution. The blanksare then treated with a salt, such, for example, as common table salt(sodium chloride having one per cent magnesium carbonate). This step maybe performed, for example, by dipping the blanks in a solution made bydissolving approximately 2% ounces of table salt in two gallons ofwater. The blanks are then dried, preferably by an air blast, whereuponthey are treated in the usual manner to produce cuprous oxide thereon.

The salt may be applied by other methods. For example, it may beintroduced into the furnace in which the blanks are given the usual heattreatment, or it may be spread on the blanks just before the blanks areoxldlzed, or it may be applied to the copper blanks by pressing theblanks against an absorbent material soaked with the salt solutlon.

The result of a large number of tests of the sodium chloride treatmentshows a substantial increase in rectification ratio, this belngaccomplished by a decrease in the electrical resistance in bothdirections, the decrease being greater in the low resistance than in thehigh resistance direction.

As another example, the cleaned blanks may be dipped in a water solutionof potassium iodide, one'efiect of which is to increase the electricalresistance of the finished rec- In its broader aspect, my inventionconsists 1n treatin a rectifier blank with a water solution a salt, theterm salt when used Application filed October 9, 1929. Serial No.398,576.

in this sense being taken to mean any chemiunited with one or more atomsof metals.

Having thus described my invention, what I claim is:

l. The method of preparing copper blanks for the manufacture of copperoxide rectifiers which consists in dipping the blanks in a solution madeby dissolving a proximately two and one-half ounces of ta le salt inapproximately two gallons of water.

2. The method of preparing copper blanks for the manufaceure of copperoxide rectifiers which consists in dipping the blanks in a sodiumchloride solution.

3. The method of preparing copper blanks for'the manufacture of copperoxide rectifiers which consists in treating the blanks with sodiumchloride.

In testimony whereof I afiix my signature.

' PAUL H. GEIGER.

cal compound consisting of an acid radical

